What happens when a yellow brake inhibit light is illuminated?

When the yellow brake inhibit light is illuminated, it indicates that the Emergency Pneumatic (EP) brake system has automatically engaged, replacing the Emergency Dynamic (ED) brake. This scenario typically occurs to ensure the train can still stop safely when there is a fault or issue with the ED brake. The EP brake is a backup system designed to maintain braking capability under certain failure conditions, allowing for safer operations.

In contrast, if the yellow brake inhibit light were to indicate that the speed of the train increases, it would imply a complete failure of the braking systems, which contradicts the purpose of safety features. As for failing completely, the systems are designed to engage backups rather than result in a total failure of brakes. If stopping the train entirely were necessary, it would not be managed solely by the illumination of this particular warning light; instead, operational procedures would dictate how to proceed safely. Thus, the illumination points to the train's capability to manage its braking through an alternative system rather than signaling immediate danger or a complete loss of function.